In an LTE (Long Term Evolution, Long Term Evolution) TDD (Time Division Duplexing, time division duplexing) system, due to asymmetry of uplink and downlink, when there are more downlink subframes than uplink subframes, feedback information (for example, ACK or NACK information) of a plurality of downlink subframes is sent together in a same uplink subframe. Here, downlink subframes whose feedback information is sent in a same uplink subframe are referred to as a binding window.
A CA (Carrier Aggregation, carrier aggregation) technology is introduced in LTE release 10. Each cell where the CA technology is adopted adopts the same TDD uplink and downlink configuration. Therefore, each cell can work according to a HARQ (Hybrid Automatic Repeat reQuest, hybrid automatic repeat request) timing relationship of the TDD uplink and downlink configuration defined in LTE release 8. LTE release 10 specifies that feedback information of a PDSCH (Physical Downlink Shared Channel, physical downlink shared channel) of each cell is sent by a primary cell (PCell), which ensures the single-carrier characteristic for an uplink signal and also simplifies power control on the uplink signal. As all cells adopt the same TDD uplink and downlink configuration, within a same uplink subframe, the number of subframes whose feedback information needs to be sent by a primary cell is the same as the number of subframes whose feedback information needs to be sent by a secondary cell (SCell). Therefore, a same method may be adopted to process feedback information of each cell, so as to send the feedback information based on a channel selection mapping table.
In LTE release 11, the problem that a TDD system coexists with an existing system in each frequency band and requirements such as a heterogeneous network are considered, and a processing method for a case that a plurality of cells adopting the CA technology have different uplink and downlink configurations needs to be researched. In other words, in LTE release 11, within a same uplink subframe, the number of subframes whose feedback information needs to be sent by a primary cell may be unequal to the number of subframes whose feedback information needs to be sent by a secondary cell. Therefore, how to send feedback information when a plurality of cells adopting the CA technology have different uplink and downlink configurations is an urgent problem to be solved.